The present invention relates to a taper implant, a screw-fastening structure using a taper implant with female threads, a forming drill for drilling an insertion hole for the taper implant, and a hammer for driving the taper implant.
Generally, often inserted or press-fitted into a soft base member, such as an aluminum plate, are those other members which are harder than the base member and have an axis perpendicular to the surface of the base member. For example, when female threads are tapped in an aluminum plate and this aluminum plate is fastened to another plate by using a male stainless screw, chips are generated and fall from the aluminum female threads upon the male screw being tightened into a hole with the female threads in the aluminum plate. If a falling of chips is not desired as, e.g., in the assembly step of electronic devices and units, a reinforcing member is often inserted into the hole with the female threads in the aluminum plate. Such a reinforcing member is in the form of a coil spring made of stainless steel having strength comparable to the male screw and being rhombic in cross-section. The reinforcing member is inserted into a threaded hole tapped beforehand to be fit with an outer periphery of the reinforcing member, and a male screw is inserted into the threaded hole along an inner periphery of the reinforcing member. The use of the reinforcing member prevents generation of chips because the male screw contacts the stainless reinforcing member.
As another example, a stainless positioning pin is sometimes press-fitted into a hole drilled in an aluminum plate.
However, when a reinforcing member is inserted into a hole of an aluminum plate, insertion of the reinforcing member requires a skill. More specifically, in the case of inserting the reinforcing member with a tool, while rotating it, into a threaded hole tapped to be fit with an outer periphery of the reinforcing member, the inserted reinforcing member may skip some threads of the threaded hole, or it may deform into a conical shape (as the reinforcing member is inserted, the inner diameter of its lower portion is gradually reduced), unless the worker is skilled. This has raised the problem that the process of inserting the reinforcing member is poor in working efficiency.
Also, when a stainless positioning pin is inserted into a hole of an aluminum plate, the positioning pin may be inserted obliquely with respect to the aluminum plate due to deformation of the aluminum plate, for example, unless the worker is skilled. This has raised the problem that the process of inserting the positioning pin is poor in working efficiency.
An object of the present invention is to provide a taper implant, a screw-fastening structure using a taper implant with female threads, a forming drill for drilling an insertion hole for the taper implant, and a hammer for driving the taper implant, each of which ensures good working efficiency.
To achieve the above object, a taper implant according to the present invention comprises a taper portion having an outer surface being frusto-conical in shape, and a projecting portion formed at an outermost end of the taper portion on the larger-diameter side to project outward with respect to the taper portion, and having a flat surface lying perpendicularly to the axial direction of the taper portion. In a preferable form, the projecting portion is a diskshaped flange portion which is uniformly projected outward from the outer surface of the taper portion. The taper implant further comprises a fit portion extending in the axial direction of the taper portion. With such a construction, just by dropping the taper implant into a hole bored in one of members to be fastened and having a hole taper portion, and then driving the taper implant into the hole by hitting the side of the flange portion, the taper portion and the flange portion are press-fitted to an inner wall surface of the hole bored in the fastened member, enabling the taper implant to be easily fixed to the fastened member, while the taper implant is prevented from overly thrusting into the hole. As a result, the working efficiency is improved.
Also, to achieve the above object, in screw-fastening structure using a taper implant with female threads according to the present invention, a hole having a hole taper portion gradually spreading toward a larger-diameter opening is drilled in a first member, a taper implant having a taper portion including female threads tapped therein beforehand is fitted to the hole taper portion, and a male screw is inserted and tightened into the female threads from the side of a second member, whereby the first and second members are fastened to each other. With that structure, the work of fastening two members to each other can be performed with high efficiency.
Further, to achieve the above object, in a forming drill for drilling an insertion hole for a taper implant according to the present invention, the drill integrally includes a taper portion drilling bit for boring a hole into which a taper portion of the taper implant is to be inserted, and a step portion drilling bit for boring a hole into which a projecting portion of the taper implant is to be inserted, and a hole taper portion and a hole step portion of the hole are drilled in a member at the same time by the integral bits of the drill. With such a construction, control of tight-fit accuracy of the taper implant can be facilitated.
In addition, to achieve the above object, a hammer for driving a taper implant according to the present invention comprises a piston pushed forth by a compression spring, and opening/closing means for selectively opening and closing an exhaust port communicating an air chamber with the outside, the exhaust port having a sectional area set larger than a sectional area of an air supply port through which compressed air is introduced to the air chamber, the piston being pushed back against biasing force of the compression spring by the compressed air introduced to the air chamber. With such a construction, the taper implant can be driven under driving force so reduced as to prevent damage of the fastened member, and the piston can be automatically pushed back to its start position. As a result, the work of driving the taper implant can be easily performed.